Fuse holder and circuit disconnect device



April 4, 1950 w. P.' KELLER FUSE HOLDER AND CIRCUIT DIscoNNEcT DEVICE Filed June 22, 1949 ATTORNEYS. v

Patented Apr. 4, 1950 DEVI Walter P. Keller, Chicago, Ill. Application J une 22, 1949, Serial No..100,5.77

2-Claims. 1

This invention relates to a greatly improved fllSe'hOlder which can also be conveniently em ployed'as a safe and certaincircuit disconnect device.

Ever since the general adoption of fuses as circuit protective devices, a great need has existed fora satisfactoryfuse holder. Fuse holders heretofore employed have had serious disadvantages, both from the standpoint of convenience 'andsafety.

In fact, the inadequacy of prior-art fuse holders as been in large part responsible for the extensive use ofcircuit breakers, notwithstanding their much higher cost as compared to thermal fuses.

Most'thermal fuses employed in'industrial and commercial electrical installations are of the This type of construction is cartridge" type.

from thestandpoint of fuse highly desirable manufacture, since it is inexpensive and welladapted to mass production.

Theonly fuses in general use which are not ofthe cartridge type are the screw-base fuses commonly used in home lighting circuits. The screw-base fuse is muchmore expensive to constructthan the cartridge fuse, and it" is frequently" unsatisfactory in service because, first, circuit failure often results from imperfectcontactd'u'e to loose insertion and, second, theopen receptacle into which the fuse is to be inserted iri'vites accidental shock.

In spite of the shortcomings just described,

the screw-base fuse has nevertheless remained in eneral use for home electrical installations simply because it has been, with. all its disadvantages, safer in unskilled hands than the.cartridge fuse asemployed with any oftheprior-art fuse holders.

An important objectof my present invention is to provide a fuse holder for cartridge fuses which is entirely safe in use, even when being handled by totally inexperienced persons.

Another object of my present invention is to provide a fuse holder with which fuses can be.

replaced with complete safety from shock and without the necessity for opening; a master line switch. This advantage of my. present inventionv isof great practical importance, since changing a fuse in prior-art practice, whether the fuse.

be of the cartridge or screw-base typahas always required that the master line switchv be open. This has usually resulted in temporary interruption of electric service to a number of.

circuits other than the one affected by the fusev to b'er'epla'ced. The inconvenience and lack of has, as apractical matter, been particularly ob-- je'ctionable in apartment fice buildings.

A further object of my invention is to provide a fuse holder physically removable in its entirety from the electrical circuits with which it is normally associated; This feature yields two important advantages-first, it insures that at' the time the fuse is replaced, no possibility of shock can exist, and, second, it permits replacement of the fuse at a place and under conditions of light which are convenient rather than compelling the person replacing the fuse to fumble dangerously about a fuse box in a dark corner of an engine room or an apartment house basement. This feature of my invention represents a great forward step over prior-art cartridge fuse holders. Those in prior use have, for the most-part, consisted of openspring clamps mounted within a fuse box. Optimum adjustment of the spring clamps has always been an almost impossible task. If the spring tension be made great enough to insure positive contact with the fuse terminals, then manual removal ofthe fuse without the use of tools is almost impossible. On the other hand, if the spring tension'be adjusted to permit easy houses, hotels, and of-' manual removal, the contact with the fuse ter-' minals is uncertain and likely to fail after a few weeks accumulation of dirt'and oxide has formed on the spring contacts and the fuse terminals.

Another importantobject of my invention is to obviate the last-mentioned accumulation of foreign matter, oxide, dirt, etc. on the contact surfaces and the fuse terminals; with my present invention, the fuse is held at all times in firm contact with the holder electrodes and at the same time wholly enclosedfor protection against access of foreign; matter. Moreover, circulation of air around the fuse terminals and electrodes is effectively prevented, thus inhibiting oxidation almost completely.

Still another object ofmy invention is to provide a fuse. holder having a protective casing which can be disassembled at will, without tools, for the replacement or removal of a fuse and.

Still another object of my invention is to provide a fuse holder for cartridge fuses having no electrical conductors externally accessible by manual contact and yet providing convenient means for testing the continuity of the fuse with.- out physical removal of the fuseholder.

Other objects and advantages of my invention will appear as the specification proceeds.

An illustrative embodiment of my invention is illustrated in the accompanying drawing, of which Figure l is a perspective view of a fuse holder made'in accordance with my invention; Fig. 2, a view in side elevation of the fuse holder of Fig.1, the holder being shown mounted within a wall receptacle adapted to receive it; Fig. 3, a top plan view of the fuse holder of Fig. '1 as it appears with the cap removed; Fig. 4, a bottom view of the fuse holder of Fig. 1; Fig. 5, a sectional view of my fuse holder, the section being axial and in a plane perpendicular to thecontact prongs; Fig. 5 also shows diagrammatically circuit connections to illustrate the manner of insertion of my fuse holder in an electrical circuit; Fig. 6, a sectional view similar to Fig. 5 but differing therefrom. in that the cap, the fuse, and the removable electrode shown in Fig. 5 have beenremoved; Fig. 7 is a sectional view taken through the base of my fuse holder along the line '7-1 of Fig. 5; and Fig. 8, a sectional view through the body portion of my fuse holder along the line 8-8 of Fig. 5.

As may be seen from the figures, the embodiment of my invention illustrated. in the drawing has a body portion. Ill of generally tubular shape. The lower end of body I merges into an annular shoulder ii, formed integrally with body It. The upper end of body If! is provided with threads I? adapted for co-operation with corresponding internal threads on. cap member I3.

The body portion II], with its lower annular shoulder I I, are made of insulating material and, in the normal case, will be integrally molded from a plastic :naerial such as hard rubber or Bakelite. Similarly, the cap [3 is formed of insulating material and, like the body member ID, is preferably molded from. a plastic material.

As may be best observed from Figs. 5 and 6, body member I0 of my fuse holder is provided with an axial hollow portion iii of cylindrical shape and of size adapted to receive readily the particular fuse to be carried by the fuse holder. Central opening I5 is open at the upper end of body l0; it extends at its lower end to a pointnear the bottom of base shoulder II, but a re-- taining wall or floor Ha provides a bottom for central opening or fuse socfret I5.

A metal contact prong I4 is securely locked within the base shoulder II, preferably by being molded in at the time body member ID and base shoulder H are originally formed. Contact prong I4 is provided with an orthogonally disposed portion Ma which, as is best shown in Figs. 5, 6, and '7, entirely covers the inner surface of wall Ila and thus provides a contact electrode for the lower terminal of fuse I6 when it rests within socket I5. A detent I Ib may be provided on the shank of prong I4 to assist in securing it in its socket. 5 In a plane parallel to the plane occupied by the prong portion of member I4, body member I0 is equipped with a slot I'I extending entirely through body member I0 and base shoulder II. The wall I8 which separates slot I! from fuse socket I5 is relieved for a short distance at its upper end so as to provide a communicating passage between slot I1 and socket I5 below the topmost extremity of the body member proper. This last-mentioned construction is clearly shown in Figs. 5 and 6.

A metal electrode member I9 comprises a straight shank portion formed and shaped for cooperation with slot I1 and an orthogonally disposed portion l9a. Member l9a should preferably be rounded at its terminal portion, as shown in Fig. 3, to seat readily within fuse socket I5.

As may be seen from Fig. 5, prong member I9, when my fuse holder is assembled for use, is' received within slot I1, the length of the shank portion of prong member I9 being such that it extends outward beyond the bottom portion of base shoulder II to form a contact prong sub stantially equal in length to prong l4.

The prongs I4 and I9 are adapted to be plugged into a suitable electrical. receptacle; an illustrative receptacle H is shown in Fig. 2, mounted within a terminal box or casing 22. It will be understood that the dimensions of prongs I4 and,

. I9 may be varied within wide limits to adaptmy 3F fuse holder to a particular type of receptacleor to adapt it for handling currents of various magnitudes. It will be obvious to anyone skilled in the art that anembodiment of my fuse holder adapted to carry, for example, a 100 ampere fuse in heavy duty service would be provided with more massive prong members I9 and III than would be appropriate for an embodiment of my fuse holder intended for domestic household service with a or ampere fuse.

A small aperture 23 is provided in cap member I3; the thickness of cap member l3, while not critical, should be sufficiently great to prevent any manual contact with electrode Illa through aperture 23. Aperture 23 is intended to aCcommodate a test probe for purposes which will be more fully described in a succeeding paragraph hereof.

In the replacement of a fusein my fuse holder, the operator first graspsmy fuse holder by the receptacle within which it is carried. This operation entails absolutely no danger of shock, since no manual contact with any conducting material is involved in the removal of my fuse holder. from its receptacle. l The cap I3 is then unscrewed from body mem-.

ber I0, and prong member I9 is removed. This last operation may be accomplished merely by holding the fuse holder in a bottom-up positionf 5 member I9 will thereupon fall out of slot ll bjy force of gravity. Fuse I6 may thereupon be easily removed from fuse socket I5 and replaced with a suitable renewal fuse. After the new fuse I6 is seated within socket l5, as shown in Fig. 5, 7o electrode member I9 is thereupon returned to slot l1 and seated firmly in position with the orthogonally disposed electrode Ida making face-tr. face contact with the upper terminal of fuseflt. Cap member I3 is thereupon screwed backflintfo. "15 place onbody member I0; cap I3 is thus pressed body it and physically withdraws it from the with a firm and positive force against electrode I9a. This force is in turn transmitted through fuse IE to electrode Ma. Accordingly, when cap member I3 is screwed securely and tightly onto body member I0, the fuse I6 is held tightly within socket I5, secure against vibration and assured of excellent electrical contact between its respective terminals and electrodes Ma and No.

When the just-described operation has been completed, my fuse holder may then be replaced in its receptacle, once again with perfect assurance that no danger or shock exists. It should be noted that the operation involved in replac ing a fuse may be accomplished without any necessity whatever for opening a master line switch or otherwise interfering with the electrical circuit which may be supplying a number of lines other than that affected by the fuse being replaced.

It may be noted that the embodiment of my invention shown in the drawing is provided with polarized prongs-that is, the physical width of prong I9 is somewhat less than that of prong l4, so that, given a similarly-formed receptacle, my fuse holder can be inserted in only one position. While the use of polarized prongs and receptacle is a refinement which may be dispensed with if desired, its use does provide one special advantage which may be very convenient. When a polarized receptacle is employed, connections should be made as indicated diagrammatically in Fig. 5. Therein a power line, one side of which is conventionally grounded, is connected through my fuse holder to an electric motor 25. The receptacle connections should be such that prong l 4 is connected directly to the power line (on the ungrounded side, of course) while the prong I9 is connected to the motor 25. The other terminal of motor is of course connected to the grounded side of the power line. When the receptacle for my fuse holder is connected as shown in Fig. 5, the aperture 23 may be very conveniently employed, in conjunction with a test probe, to determine whether the fuse within the holder is good or bad. Fuses are normally tested by using a light bulb or other indicating source connected in series between ground and the test probe. If such apparatus is employed with my fuse holder, the test probe may be inserted through aperture 23 and thus brought in contact with electrode I9a. If the fuse is good, the test light will glow; if the fuse is bad, there will be no indication from the test light, since the circuit will be broken between the hot side of the line and electrode l9a.

As may be seen from the structural advantages herein described, the normal function of my invention as a fuse holder may be supplemented by the additional function of circuit disconnect device. It will be obvious to those skilled in the art that my invention can readily be formed in tandem or in triplicate units; such construction would merely involve the molding in a single piece of as many body members It] as might be desired, they being joined one to another by an integral base member ll. Such a double or triple fuse holder unit could be easily designed for co-operation with a double or triple receptacle; such receptacles are well known and in general use. Such a tandem or three-unit fuse holder could thus be readily connected to a single-phase or three-phase power line so as to fuse each leg of the line and, upon removal of the fuse holder, to disconnect each leg of the line. My invention could thus safely and inexpensively replace the complicated and expensive knife switches which are in general use as main line switches today. Moreover, since my invention is inherently shock-proof, the elaborate means customarily employed for protecting the user of such knife switches against shock can be dispensed with entirely.

While I have in this specification described in considerable detail a particular illustrative embodiment of my invention, it is obvious that persons skilled in the art may introduce many variations in details without departing from the spirit of my invention; it is accordingly my desire that the scope of my invention be not limited to the particular embodiment shown and described herein but that such scope be determined solely with reference to the appended claims.

I claim:

1. A fuse holder comprising a cylindrical body member having an axial socket therein for receiving a cartridge fuse and having also a slot adjacent said socket, said socket having a bottom wall and an open end opposite thereto, an electrode member mounted in the end of said body member adjacent said bottom wall, said electrode having a base portion extending across said bottom wall and a shank portion extending externally from the bottom of the body member to form a contact prong, an electrode member for the open end of the socket adapted to make electrical contact with the outer terminal of a cartridge fuse received within the socket, the inner terminal of such fuse being pressed against said bottom wall electrode member, said openend electrode member having an elongated shank adapted to be removably received in said slot and to extend therefrom externally to the body member when said electrode is seated against the fuse terminal and to form a contact prong, adapted with said first-mentioned contact prong to be plugged into a receptacle, and locking cover means for the body member adapted to close off the open end of the socket and, when in locking position, to clamp the fuse between said two electrodes by applying force between said openend electrode and the body member, the external portions of said body member and the locking cover being formed entirely of insulating material.

2. A fuse holder according to claim 1 wherein a small hole is provided in the locking cover to permit access with a test probe to the electrode therebelow while preventing manual access to the electrode so long as the cover is in locking position.

WALTER P. KELLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,028,258 Murray June 4, 1912 1,552,971 Unger Sept. 8, 1925 1,631,178 Wurdack June 7, 1927 1,966,716 Green July 17, 1934 2,289,358 Hanny July 14, 1942 

